An engine starting and charging device including a starting motor and a charging generator as one unit has been suggested as a prior art, for example, as disclosed in Laid-Open Japanese Patent No. Sho 61-54949.
FIG. 1 is a sectional view of a prior-art engine starting and charging device disclosed in Laid-Open Japanese Patent No. Sho 61-54949. In FIG. 1, a starting and charging device body 1 comprises revolving field poles 2a, 2b, a field coil 3, an armature core 4, an armature coil 5, and a crank angle detector 6 as major components.
The revolving field poles 2a, 2b are a pair of comb-shaped field poles produced of a ferromagnetic material, which are coupled as a unit through a ring 7 of a non-magnetic material such that their magnetic pole sections are arranged alternately in the circumferential direction. The field pole 2a, functioning as a flywheel and also as a clutch carrier described later, is mounted on an engine crankshaft 8, and fixed on the end of the crankshaft 8 by a bolt 9. Numeral 10 is a cutout formed at the side section of the field pole 2a, which, combined with the crank angle detector 6, is used to detect the crank angle; the same number of cutouts as the number of magnetic poles of the field pole 2a are provided at equal intervals around the circumference. The width of the cutout 10 in the circumferential direction makes an angle equal to about one half of 360 degrees divided by the number of the cutouts.
The field coil 3, which is for exciting the field poles 2a, 2b, is mounted on the field core 11. This field core 11 is mounted and fixed to a bracket 12 by bolts, which are not illustrated, facing the field poles 2a, 2b, across slight air gaps a, b in the radial direction.
The armature core 4 is formed by laminating silicon steel sheets, within the inner periphery of which are provided a number of slots for setting the armature coil 5 therein, the armature coil 5 being of a three-phase distributed winding type as a common commutatorless brushless motor. The armature core 4 is properly positioned and fixed in relation to the bracket 12, which is secured by bolts 15 to an engine body 13 together with a housing 14 for securing the armature core 4.
The crank angle detector 6 functions as a signal source that operates an armature current switching circuit which is not illustrated, and uses an oscillation-type proximity switch. This proximity switch is so mounted on the bracket 12 that its detecting element faces on the circumferential line where the cutouts 10 of the field pole 2a are provided, and its oscillating conditions vary with the change of inductance at the cutout and non-cutout sections of the field pole 2a, outputting a binary signal "1" and "0" corresponding to the crank angle (field pole position). When a three-phase armature coil 5 is employed, there will be installed three crank angle detectors 6.
Clutch 16 interrupts the transmission of power between the crankshaft 8 and a transmission drive shaft 17, and uses a diaphragm spring clutch comprising a clutch disc 18, a pressure plate 19, a diaphragm spring (disc spring) 20, wire rings 21, 22, and a clutch cover 23. The clutch cover 23 is mounted by bolts 24 to the field pole 2a.
The clutch 16, as is well known, is of such a constitution that when a clutch pedal (not illustrated) is not depressed, the tension of the diaphragm spring 20 is exerted, by leverage, to the clutch disc 18 mounted on the transmission drive shaft 17 through the pressure plate 19, pressing this clutch disc 18 against the side of the field pole 2a to connect the clutch.
When the clutch pedal is depressed, a sleeve, which is not illustrated, slides in the axial direction, pressing the central part of the diaphragm spring 20 in the direction of the arrow C. Therefore the diaphragm spring 20 deflects back on the wire rings 21, 22 as a fulcrum, thus removing a pressure that has been exerted to the clutch disc 18 to disconnect the clutch, and accordingly shutting off the transmission of power from the crankshaft 8 to the transmission drive shaft 17.
In operation, when the key switch, which is not illustrated, is turned to the START position, with the engine left stationary, the current flows into the field coil 3 and the armature coil 5, thereby producing a torque at the field poles 2a, 2b to turn the crankshaft 8 directly coupled. When the field poles 2a, 2b have started turning, the crank angle detector 6 detects the positions of the field poles, and the armature current switching circuit switches the current to the armature coil 5 so that the speed of a rotating field formed by the armature coil 5 will be the same as the speed of rotation of the field poles; accordingly the field poles 2a, 2b will gain a torque for further acceleration. The device, thus producing a starting torque by such a positive feedback operation, starts the engine.
After the engine has started, the speed of rotation of the field poles further increases, thus increasing a back electromotive force produced at the armature coil 5; accordingly no unnecessary starting current will flow.
Furthermore, when, after the starting of the engine, the key switch is placed in the IGNITION position, the starting and charging device body 1 operates as an a.c. synchronous generator, which produces the electric power. The electric power thus produced is converted into d.c. power by means of a rectifier which is not illustrated, and supplied to the battery and electrical equipment mounted on the motor vehicle.
As described above, the prior-art starting and charging device body 1 is disposed between the engine body 13 and the clutch 16. However, since the engine crankshaft 8 and the transmission drive shaft 17 are usually disposed in series, the engine becomes longer in the axial direction than in the radial direction; particularly in an automobile mounted with a horizontal engine which has little dimensional room in the axial length, it is difficult to mount the starting and charging device between the engine body 13 and the clutch 16.
In the case of an engine equipped with a special starting motor and a charging generator, these equipment are mounted in parallel in relation to the engine body. Therefore, there is such a problem that the application of the aforementioned prior-art starting and charging device to such an engine requires a substantial modification in the arrangement of various parts of the engine.